Amorphous Alloys on the Base of Zr and their Use

ABSTRACT

An alloy is disclosed which contains at least four components. The alloy has a bulk structure containing at least one amorphous phase. The alloy composition follows an “80:20 scheme”, i.e., the alloy composition is [(A x D 100−x )a(E y G 100−y ) 100−a ] 100−b Z b  with the number “a” being approximately 80. Preferably, component A is Zr. The other components D, E, G and, optionally, Z are all different from each other and different from component A. A preferred system is Zr—Cu—Fe—Al. Further disclosed are Cu-free systems of the type Zr—Fe—AI-Pd/Pt. Importantly, the alloy is substantially free of nickel. This makes the alloy especially suitable for medical applications. Methods of preparing such an alloy, uses of the alloy and articles manufactured from the alloy are also disclosed.

FIELD OF THE INVENTION

The present invention relates to an alloy with the features of thepreamble of claim 1 or 19, to the use of such an alloy, and to articlesmanufactured from such an alloy, in particular implants such asendoprostheses.

BACKGROUND OF THE INVENTION

A number of alloys may be brought into a glassy state, i.e., anamorphous, non-crystalline structure, by splat cooling at very highcooling rates, e.g., 10⁶ K/s. However, most of these alloys cannot becast into a bulk glassy structure at much lower cooling rates achievablewith casting.

In recent years, many bulk metallic glass-forming liquids have beendiscovered for which cooling rates of less than 1000 K/s are sufficientfor vitrification. For the purposes of this document, a “bulk metallicglass” is to be understood as an alloy which develops an at leastpartially amorphous structure when cooled from a temperature above themelting point to a temperature below the glass-transition temperature ofthe amorphous phase with a cooling rate of 1000 K/s or less, preferablywith a cooling rate of 100 K/s or less. Cooling rates in this range aretypically experienced in bulk casting operations.

Bulk metallic glasses generally have mechanical properties that aresuperior to their crystalline counterparts. Due to the absence of adislocation mechanism for plastic deformation, they often have a highyield strength and elastic limit. Furthermore, many bulk metallicglasses show good fracture toughness, corrosion resistance, and fatiguecharacteristics. For an overview of the properties and areas ofapplication of such materials see, for example, Johnson W L, MRS Bull.24, 42 (1999) and Löffler J F, Intermetallics 11, 529 (2003). Referenceis made explicitly to the disclosure of these documents and thereferences cited therein for teaching properties of glass-formingmetallic alloys and methods for the determination of such properties.Commercial applications of bulk metallic glasses are described, e.g., inBuchanan O, MRS Bull. 27, 850 (2002).

Currently, only Zr-based bulk metallic glasses (and some Pt-basedglasses for jewelry) have found their way into applications. Thefollowing documents of the prior art deal with Zr-based glass-formingalloys:

-   -   U.S. Pat. No. 5,740,854 discloses an alloy of composition        Zr₆₅Al_(7.5)Ni₁₀Cu_(17.5).    -   U.S. Pat. No. 5,288,344 discloses alloys of general composition        Zr—Ti—Cu—Ni—Be. Specifically, the alloy        Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni₁₀Be_(22.5), which has become known        under the trade name Vitreloy 1™ or Vit1™, and        Zr_(46.75)Ti_(8.8)Ni₁₀Cu_(7.5) Be_(27.5), which is known under        the trade name Vitreloy 4™ or Vit4™, are disclosed in that        document.    -   U.S. Pat. No. 5,737,975 discloses alloys of the general        composition Zr—Cu—Ni—Al—Nb. Specifically, an alloy of        composition Zr₅₇Cu_(15.4)Ni_(2.6)Al₁₀Nb₅, which is known under        the trade name Vitreloy 106™ or as Vit106T, is disclosed in this        document.    -   Lin X H, Johnson W L, Rhim W K, Mater. Trans. JIM 38, 473        (1997)) discloses the alloy Zr_(52.5)Ti₅Cu₁₇₉Ni_(14.6)Al₁₀, also        known as Vit105™.    -   Löffler J F, Bossuyt S, Glade S C, Johnson W L, Wagner W,        Thiyagarajan P, Appl. Phys. Lett. 77, 525 (2000) and Löffler J        F, Johnson W L, Appl. Phys. Lett. 76, 3394 (2000) describe        comparative investigations of Vit1™, Vit105™ and Vit106™.

Kündig A A, Löffler J F, Johnson W L, Uggowitzer P J, Thiyagarajan P,Scr. mater. 44, 1269 (2001) describes alloys of the general formulaZr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10−x)Ti_(5+x), i.e., alloy compositionswhich have been varied in the vicinity of the composition of Vit105™.

-   -   Inoue A, Shibata T. and Zhang T., Mater. Trans. JIM 36,        1426 (1995) discloses alloys of composition        Zr_(65−x)Ti_(x)Al₁₀Cu₁₅Ni₁₀.    -   Zhang T, Inoue A, Mater. Trans. JIM 39, 1230 (1998) discloses        alloys of composition Zr_(70−x−y)Ti_(x)Al_(y)Cu₂₀Ni₁₀.    -   Xing L Q, Ochin P, Harmelin M et al, Mat. Sci. Eng. A220,        155 (1996) discloses, inter alia, an alloy of composition        Zr₅₇Cu₂₀Al₁₀Ni₈Ti₅, as well as other Zr—Cu—Al—Ni—Ti alloys.    -   Löffler J F, Thiyagarajan P, Johnson W L, J. Appl. Cryst. 33,        500 (2000) describes Zr—Ti—Cu—Ni—Be alloys whose (Zr, Ti) and        (Cu, Be) contents were varied between the compositions of Vit1™        and Vit4™.    -   Inoue A, Zhang T, Nishiyama N, Ohba K, Masumoto T, Mater. Trans.        JIM 34, 1234 (1993) discloses an alloy of composition        Zr₆₅Al_(7.5)Cu_(17.5)Ni₁₀.

According to the following documents, the addition of Fe to anZr—Al—Ni—Cu alloy was believed not to improve or to even decrease theglass-forming ability:

-   -   Inoue A, Shibata T, Zhang T, Mater. Trans. JIM 36, 1420 (1995).    -   Eckert J, Kubler A, Reger-Leonhard A et al, Mater. Trans. JIM        41, 1415 (2000).    -   Mattern N, Roth S, Kuhn U et al, Mater. Trans. JIM 42, 1509        (2001).

Due to their favorable mechanical properties, bulk metallic glasses areinteresting candidate materials for biomedical applications. However,most known glass-forming alloys, especially Zr-based alloys, contain aconsiderable proportion of nickel (Ni). Exposure to nickel is known topossibly cause allergies. Therefore these alloys are not well suited formedical applications, in which the alloy can come into contact with bodyfluids, with the skin, with tissue or other body parts. Specifically,these alloys may cause allergic reactions because they tend to releasesmall amounts of nickel when they come into a prolonged contact with thebody. Copper (Cu) may also be problematic, albeit to a lesser extent.

Fan C, Inoue A, Mater. Trans. JIM 38, 1040 (1997) describes theimprovement of mechanical properties by precipitation of nanoscalecompound particles in Zr—Cu—Pd—Al amorphous alloys. However, thesealloys are not bulk metallic glasses; they are only amorphous when usingmelt spinning or splat quenching.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an alloywhich has good glass-forming ability and an improved biocompatibility,in particular, an alloy which does not release nickel in contact withbody liquids.

This object is achieved by an alloy with the features of claim 1.

It is another object of the present invention to provide an alloy whichhas good glass-forming ability and an improved biocompatibility, inparticular, an alloy which is essentially free of both copper andnickel.

This object is achieved by an alloy with the features of claim 19.

Thus, an alloy is provided which contains at least four components A, D,E and G. Optionally, a fifth component Z may be present. The alloypreferably has a bulk structure containing at least one amorphous phase,i.e., a volume fraction of at least 10%, preferably at least 50% of thealloy is amorphous. In the context of this document, a structure isconsidered to be fully amorphous if the material having this structuredoes not exhibit significant Bragg peaks in an X-ray diffractionpattern. Accordingly, the volume fraction of the amorphous phase in amixed-phase material may be estimated by integrating the intensity ofBragg peaks and comparing with the intensity of non-Bragg features.

Preferably, the amorphous phase can be obtained by cooling from atemperature above the melting point to a temperature below theglass-transition temperature of the amorphous phase with a cooling rateof 1000 K/s or less, i.e., preferably the alloy is a bulk metallicglass. More preferably, the amorphous phase can be obtained by coolingwith a cooling rate of 100 K/s or less. This enables the material to beformed by casting, in particular copper-mold casting. In other words,preferably the alloy with at least one amorphous phase can be obtainedin a shape with dimensions of at least 0.1 mm, preferably at least 0.5mm, more preferred at least 1 mm in any spatial direction. This is notpossible for alloys which adopt an amorphous structure only at coolingrates as achievable by splat cooling or melt spinning.

Component A consists of at least one element selected from the groupconsisting of Zr (zirconium), Hf (hafnium), Ti (titanium), Nb (niobium),La (lanthanum), Pd (palladium) and Pt (platinum). The other componentsD, E, G and, optionally, Z are all different from each other and fromcomponent A. Each of these components may consist of more than oneelement, as long as all elements of all components are different.Preferably, however, components D, E and G each consist of a singleelement. The alloy composition follows an “80:20 scheme”, i.e., theratio of the combined atomic content of components A and D to thecombined atomic content of components E and G is approximately 80 to 20,within a band of plus or minus 10, preferably a band of plus or minus 5,in particular a band of plus or minus 2.

Expressed as a chemical formula, the alloy composition is

[(A_(x)D_(100−x))_(a)(E_(y)G_(100−y))_(100−a)]_(100−b)Z_(b),

where x, y, a and b are independent numbers selected from zero and thepositive real numbers and denote atomic percentages, with 70≦a≦90,preferably 75≦a≦85, more preferred 78≦a≦82. The following example ismeant to illustrate the meaning of the term “atomic percentage”: Beforemultiplying indices outside and inside of brackets, the indices insidethe brackets should be divided by 100, e.g.,(Zr_(72.5)Cu_(27.5))₈₀(Fe₄₀Al₆₀)₂₀═Zr₅₈Cu₂₂Fe₈Al₂. After all bracketshave been removed, each index indicates the number of atoms contributingto a formula unit of the alloy. In the present example, 58 atoms of Zrwould be combined with 22 atoms of Cu, 8 atoms of Fe and 12 atoms of Alin order to arrive at one formula unit. In other words, if a number isan “atomic percentage”, this means that the number, when divided by 100,indicates the stoichiometry in the sense as it is usually understood inchemistry.

Component A is the main component of the alloy, in the sense that x≧50.In order to have a significant content of component D, preferably x≦95and more preferably x≦90. Advantageously, the content of component Grelative to component E is not too small, preferably y≧5, more preferredy≧10. On the other hand, the content should not be too large. Preferablyy≦95, more preferred y≦90. If a fifth component Z is present at all,then it is present in a comparatively small proportion only. In numbers,0≦b≦6, preferably 0≦b≦4, more preferably 0≦b≦2. The numbers x, y, a andb are generally independent of each other.

Importantly, the alloy is substantially free of nickel. In the contextof this document, “substantially free of nickel” means that the totalnickel content of the alloy is less than 1 atomic percent, preferablyless than 0.1 atomic percent. It may even be required that the nickelcontent is below 10 atomic ppm, e.g., in medical applications. Inparticular, none of the components A, D, E, G or Z should comprisenickel.

Preferably, components A and E are miscible in a wide composition andtemperature range. The term “wide composition and temperature range” isto be understood as a range extending over a temperature range of atleast 600 K and over a range of compositions spanning at least 60 at. %of either component in the liquid state and below the liquidustemperature in the A-E phase diagram. In the present example, a widecomposition range would, e.g., be the range from 20 at. % to 80 at. % ofcomponent A in the binary mixture A-E.

More preferably, components A and E are capable of forming a deepeutectic composition in the absence of other components. The term“capable of forming a deep eutectic composition” is to be understood asmeaning that, if A and E are mixed in the melt in the absence of othercomponents, there is a composition for which A and E are miscible downto the liquidus temperature, and the liquidus temperature of the mixturefor that composition has a local minimum as a function of composition.In other words, when varying the composition in a small vicinity of adeep eutectic, the liquidus temperature is higher than at thecomposition of the deep eutectic itself. Often, the liquidus temperatureof the binary mixture at the deep eutectic will additionally be lowerthan the melting point of each of the components taken alone. As anexample for a very deep eutectic, for A=Zr, the melting temperature isT_(m)(Zr)=2128 K, for E=Fe, it is T_(m)(Fe)=1811 K; an eutectic occursat 1201 K=0.66 T_(m)(Fe); likewise, for T_(m)(Au)=1337 K, T_(m)(Si)=1687K, and an eutectic is at 636 K=0.47 T_(m)(Au).

Preferably, the components are chosen such that a deep eutecticcomposition of the A-E mixture occurs at a composition A_(a′)E_(100−a′)with 70≦a′≦90, preferably 75≦a′≦85. Then the number a is preferablychosen such that the absolute value of the difference between a and a′is smaller or equal to 10 (i.e., |a−a′|≦10), preferably |a−a′|≦5.

Preferably, also components A and D are miscible over a wide temperatureand composition range. More preferably, they are capable of forming adeep eutectic composition when mixed in a binary mixture. If componentsA and D form a deep eutectic composition at A_(x′)D_(100−x′), then x ispreferably chosen such that |x−x′|≦10, more preferably |x−x′|≦5.

Preferably, component G is miscible with component E over a widetemperature and composition range, in particular if E is at least oneelement selected from the group consisting of the transition metals, inparticular the group consisting of Fe and Co. It is then preferred thatG is capable of forming a deep eutectic composition with component A.

More preferably, components G and E are capable of forming a deepeutectic composition at E_(y′)G_(100−y′). Then y is preferably chosensuch that |y−y′|≦10, more preferably |y−y′|≦5. Alternatively oradditionally, A and G are preferably capable of forming a deep eutecticcomposition.

Preferably, the atomic Goldschmidt radius of each element in component Ais relatively large, at least 0.137 nm, preferably at least 0.147 nm,more preferred at least 0.159 nm. In particular, if the atomicGoldschmidt radius of each element in component A is at least 0.159 nm,then preferably 70≦a≦90, if this radius is at least 0.147 nm, thenpreferably 75≦a≦85, and if this radius is at least 0.137 nm, thenpreferably 78≦a≦82. In particular, this means that for Zr-, Hf-, andLa-based alloys, preferably 70≦a≦90; for Ti- and Nb-based alloys,preferably 75≦a≦85; and for Pt- and Pd-based alloys, preferably 78≦a≦82.

The components A, D, E and G may have similar atomic radii and atomicproperties. However, it is preferred that the atomic radius of eachelement in component E is smaller than the atomic radius of each elementin component A.

The atomic (Goldschmidt) radii of the elements can be found tabulated instandard textbooks or in the 2004 Goodfellow Catalog, available fromGoodfellow Inc., Huntingdon, U.K. In particular, for selected elements,reference is made to Table 1 below.

TABLE 1 Atomic Goldschmidt radii of selected elements Element Ag Al AsAu B Be C Ca Atomic radius 0.144 0.143 0.125 0.144 0.097 0.113 0.0770.197 [nm] Element Cd Ce Co Cr Cu Fe Ga Ge Atomic radius 0.152 0.1820.125 0.128 0.128 0.128 0.135 0.139 [nm] Element In Ir Hf La Mo Mg Mn NbAtomic radius 0.157 0.135 0.159 0.187 0.140 0.160 0.112 0.147 [nm]Element Nd Ni P Pb Pd Pt Rh Rb Atomic radius 0.182 0.125 0.109 0.1750.137 0.138 0.134 0.251 [nm] Element Se Si Ta Ti Sb Sn W V Atomic radius0.116 0.117 0.147 0.147 0.161 0.158 0.141 0.136 [nm] Element Y Yb Zn ZrAtomic radius [nm] 0.181 0.193 0.137 0.160

In general terms, component D is preferably at least one elementselected from the group consisting of Cu (copper), Be (beryllium), Ag(silver) and Au (gold). Specifically, if component A is at least oneelement selected from the group consisting of La (lanthanum), Pd(palladium) and Pt (platinum), component D is preferably Cu (copper). IfA is at least one element selected from the group consisting of Zr(zirconium), Hf (hafnium) and Ti (titanium), then D is preferably Cu(copper) or Be (beryllium). Both copper and beryllium have deepeutectics with Zr, Hf and Ti.

In general terms, component E is preferably at least one metal selectedfrom the group consisting of the transition metals except Ni (nickel);particularly Sc (scandium), Ti (titanium), V (vanadium), Cr (chromium),Mn (manganese), Fe (iron), Co (cobalt), Zn (zinc), Y (yttrium), Mo(molybdenum), Ta (tantalum), and W (tungsten). A transition metal isdefined as any of the thirty chemical elements with atomic number 21through 30, 39 through 48, and 71 through 80. These metals are preferredbecause of their tendency to form deep eutectics with component A andbecause of their specific electronic properties. In particular,component E is preferably at least one metal selected from Fe (iron) andCo (cobalt). These metals have empirically been found to be preferred.

Component G is preferably at least one element selected from the groupconsisting of Al (aluminum), Zr (zirconium), P (phosphorus), C (carbon),Ga (gallium), In (indium) and the metalloids, particularly B (boron), Si(silicon), and Ge (germanium). The known metalloids are B (boron), Si(silicon), Ge (germanium), As (arsenic), Sb (antimony), Te (tellurium),and Po (polonium). It is believed that the specific electronicproperties of these elements favorably influence the glass-formingability. Furthermore, the elements B, P, C, and Si have particularlysmall atomic sizes (≦0.117 nm), which contributes to a large sizedifference between the components A and G. In particular, if component Eis Fe (iron), component G is preferably selected from the groupconsisting of Al (aluminum), Zr (zirconium), P (phosphorus), B (boron),Si (silicon) and C (carbon). More preferred, if component E is Fe(iron), then component G is Al (aluminum). Then y is advantageouslychosen to be in the range from about 30 to about 50, in particularapproximately 40. Alternatively, if component E is Co (cobalt),component G is preferably at least one element selected from the groupconsisting of Zr (zirconium), Al (aluminum), B (boron), Si (silicon), Ge(germanium), Ga (gallium) and In (indium).

In a preferred embodiment, component A is Zr (zirconium) or a mixture ofZr (zirconium) with either Hf (hafnium) or Ti (titanium) or both whereinat least 80 atomic percent of component A is Zr (zirconium). It is thenpreferred that component D is Cu (copper). It has been found empiricallythat this combination leads to alloys with superior glass-formingability.

If component A is Zr and component D is Cu, it is preferred that x ischosen between 62 and 83 (i.e., 62≦x≦83), preferably 68≦x≦77, inparticular that x is approximately 72.5. If component A is Zr andcomponent D is Cu, it is further preferred that component E is Fe (iron)and component G is Al (aluminum). Then y is advantageously chosen to bein the range from about 30 to about 50, in particular approximately 40.Alloys of this composition, specifically, the alloy compositions in thevicinity of Zr₅₈Cu₂₂Fe₈Al₁₂, have been found by the inventors to belongto the best glass formers known to date.

If a fifth component Z is present, this component is preferably at leastone element selected from the group consisting of Ti, Nb, Hf.Alternatively, component Z may preferably be at least one elementselected from the group consisting of the transition metals, orcomponent Z may preferably be at least one element selected from thegroup consisting of Be (beryllium), Y (yttrium), Pd (palladium), Ag(silver), Pt (platinum), and Sn (tin). In general terms, component Z ispreferably capable of forming a deep eutectic composition with componentA.

The alloy may have a structure comprising at least one amorphous phaseand at least one crystalline phase. The volume fraction of the amorphousphase preferably is at least 10%. The amorphous and crystalline phasesshould not be macroscopically separated. Such a structure can begenerated by different means. In one approach, a composite comprisingcrystals embedded in an amorphous matrix is produced by subjecting thealloy to heat treatment at a temperature above the glass transitiontemperature. For details, see the description of the preferredembodiments below. In another approach, the alloy is subjected toelectric currents, as described, e.g., in (Holland T B, Löffler J F,Munir Z A, J. Appl. Phys. 95, 2896 (2004)), who describe thecrystallization of metallic glasses under the influence of high densityDC currents. In still another approach, the alloy composition in themelt is chosen to be initially outside the glass-forming region. Duringcooling, crystals start forming in the melt. This alters the compositionof the mixture remaining in the melt, which is shifted into theglass-forming region. Upon further cooling, a glassy matrix withembedded crystals is formed. For details, see (Hays C C, Kim C P,Johnson W L, Phys Rev. Lett. 84, 2901 (2000)). In yet another approach,development of crystals in the amorphous matrix is fostered by asuitable choice of the fifth component Z. Suitable components Z arepreferably at least one element selected from the group consisting ofTi, Nb, Ta, or at least one element selected from the group consistingof the transition metals, or at least one element selected from thegroup consisting of Be and Pd. For details, see, e.g., (He G, Eckert J,Löser W, Schultz L, Nature Materials 2, 33 (2003)).

In a preferred embodiment, A is Zr (zirconium) and D is selected fromthe group consisting of Cu (copper) and Fe (iron).

Specifically, it is preferred that A is Zr (zirconium), D is Cu(copper), and E is selected from the group consisting of Fe (iron) andCo (cobalt). Then G is preferably at least one element selected from thegroup consisting of Al (aluminum) and the metalloids. A particularlypreferred system is the Zr—Cu—Fe—Al system, i.e., A is Zr (zirconium), Dis Cu (copper), E is Fe (iron) and G is Al (aluminum). It has been foundthat alloys of this composition, when following the 80:20 concept, havefavorable glass-forming properties.

If A is Zr (zirconium) and D is Cu (copper), it is preferred that theratio of these is chosen according to 62≦x≦83. If E is Fe (iron) and Fis Al (aluminum), it is preferred that their ratio is chosen accordingto 30≦y≦50. The combination of these ranges, together with the general80:20 concept, defines a region of quaternary compounds withexceptionally good glass-forming properties.

In particular, the alloy may substantially be represented by the formula(Zr_(x)Cu_(100−x))₈₀(Fe₄₀Al₆₀)₂₀ with 62≦x≦83, in particular, with x=62,64, 66, 68, 72.5, 77, 79, 81 or 83, or by one of the formulas(Zr₉₅Ti₅)₇₂Cu₁₃Fe₁₃Al₂, Zr₇₀Cu₁₃Fe₁₃Al₃Sn₁, Zr₇₀Cu₁₃Fe₁₃Al₂Cr₂,Zr₇₀Cu₁₃Fe₁₃Al₂Nb₂, Zr₇₀Cu₁₃Fe₁₃Al₂Zn₂, (Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈Mo₂,(Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈P₂, (Z₉₅Hf₅)₇₂Cu₁₃Fe₁₃Al₂, Zr₇₀Cu₁₁Fe₁₁Al₈,Zr₇₁Cu₁₁Fe₁₀Al₈, (Zr₇₄Cu₁₃Fe₁₃)₉₀Al₁₀, Zr₇₂Cu₁₃Fe₁₃Al₂,(Zr₇₄Cu₁₃Fe₁₃)₉₈Al₂, Zr₇₃Cu₁₃Fe₁₃Al₁, Zr₇₂Cu₁₃Fe₁₃Al₂, Zr₇₁Cu₁₃Fe₁₃Al₃,Zr₇₂Cu₁₂Fe₁₂Al₄, Zr₇₀Cu₁₃Fe₁₃Al₄, Zr₇₂Cu₁₁Fe₁₁Al₆,Zr₇₂Cu_(11.5)Fe₁₁Al_(5.5), Zr₇₃Cu₁₁Fe₁₁Al₅, Zr₇₁Cu₁₁Fe₁₁Al₇,Zr₆₉Cu₁₁Fe₁₁Al₉, Zr₇₀Cu_(10.5)Fe_(10.5)Al₉, Zr₇₀Cu₁₀Fe₁₁Al₉,Zr₇₀Cu₁₁Fe₁₀Al₉, Zr₆₉Cu₁₀Fe₁₀Al₁₁, Zr₆₉Cu₁₀Fe₁₁Al₁₀, Zr₇₀Cu₁₃Fe₁₃Al₂Sn₂,Zr₇₂Cu₁₃Fe₁₃Sn₂, (Zr₇₄Cu₁₃Fe₁₃)₉₈Sn₂, (Zr₇₉Cu₂₁)₈₀(Fe₄₀Al₆₀)₂₀,(Zr₈₁Cu₁₉)₈₀(Fe₄₀Al₆₀)₂₀, (Zr₈₃Cu₁₇)₈₀(Fe₄₀Al₆₀)₂₀,(Zr₆₆Cu₃₄)₈₀(Fe₄₀Al₆₀)₂₀, (Zr₆₄Cu₃₆)₈₀(Fe₄₀Al₆₀)₂₀, and(Zr₆₂Cu₃₈)₈₀(Fe₄₀Al₆₀)₂₀.

Another system having excellent glass-forming properties if followingthe 80:20 concept is the Zr—Fe—Al—(Pd/Pt) system. This system has theadditional advantage that it is free of copper. In other words,preferably A is Zr (zirconium), D is Fe (iron), E is Al (aluminum), andG is one or both elements selected from Pd (palladium) and Pt(platinum). Specifically, excellent glass formers have been found if Gis palladium, while a slightly improved biocompatibility may result bypartially or fully replacing Pd by Pt. In this connection, it is to benoted that Pd and Pt are known to occupy the same group of the periodicsystem of elements, and have a similar (outer-shell) electronicstructure, almost the same Goldschmidt radius and a similar chemicalbehaviour. It is therefore to be expected that Pd may be replaced by Ptwithout dramatic changes in the glass-forming properties of the alloys.In these systems, it has been found to be advantageous if the atomicpercentages of Fe and Al are substantially equal. A range of good glassformers was found for 68≦x≦89 and 73≦a≦87. Particularly good resultswere achieved for 81≦x≦85, 80≦a≦83, and 65≦y≦80, in particular if G wasPd. The ratio of Al to Pd/Pt is favourably chosen according to 40≦y≦82.

Generally, it is preferred that only small amounts of additionalelements are present, i.e., 0≦b≦2. In particular, it is preferred thatb=0, i.e., that there are substantially at most trace amounts ofadditional elements present. If such elements are present, i.e., if b>0,then Z is preferably at least one element selected from the groupconsisting of Ti, Hf, V, Nb, Y, Cr, Mo, Fe, Co, Sn, Zn, P, Pd, Ag, Auand Pt.

Expressed in another way, Zr—Fe—Al—Pd/Pt system has been found to havegood glass-forming properties if conforming to the general formula

Zr_(i)(Fe_(50+ε)Al_(50−ε))_(j)X_(k)

wherein X is one or both elements selected from Pd and Pt, a, b, c and εare zero or real positive numbers signifying atomic percentages, andε≦10, i≧50, j≧19, k≧0.5 and i+j+k=100. Excellent glass-forming abilitieswere achieved in examples where X was Pd, while a slightly improvedbiocompatibility may be expected by partially or fully replacing Pd byPt, which has very similar properties as Pd. Preferred ranges are(independently or in combination) 62≦i≦77, 19≦j≦34, and ε≦2. Preferably,ε is substantially zero, i.e., the atomic percentages of Fe and Al areapproximately equal. For the best glass formers which have been found inthis system, ε is substantially zero, 66≦i≦70, 25≦j≦29 and 4≦k≦7. Thebest glass formers of this system also conform to the 80:20 concept asdescribed above.

In particular, alloys being substantially represented by one of thefollowing formulas were found to be good glass formers: An alloyrepresented by one of the formulas

Zr₆₇Fe_(13.2)Al_(13.2)Pd_(6.6), Zr_(69.7)Fe_(12.95)Al_(12.95)Pd_(4.4),Zr_(66.7)Fe_(14.45)Al₁₄₄₅Pd_(4.4), Zr_(68.3)Fe_(13.4)Al_(13.4)Pd_(4.9),Zr_(65.4)Fe_(14.85)Al_(14.85)Pd_(4.9),Zr_(62.3)Fe_(16.7)Al_(16.7)Pd_(4.3),Zr_(59.2)Fe_(18.3)Al_(18.3)Pd_(4.2), Zr₇₂Fe_(11.5)Al_(1.5)Pd₅,Zr_(73.4)Fe_(10.9)Al_(10.9)Pd_(4.8),Zr_(75.2)Fe_(10.2)Al_(10.2)Pd_(4.3), Zr₇₇Fe_(9.5)Al_(9.5)Pd₄,Zr_(67.9)Fe_(11.8)Al_(1.8)Pd_(8.5), Zr₆₅Fe_(11.4)Al_(11.4)Pd_(12.2),Zr_(62.5)Fe_(10.75)Al_(10.75)Pd₁₆,

by the formula Zr_(i)(Fe₅₀Al₅₀)₃₀Pd_(70−i) with 62≦i≦69.5, in particularby one of the formulas Zr_(69.5)Fe₁₅Al₁₅Pd_(0.5), Zr₆₉Fe₁₅Al₁₅Pd_(0.5),Zr₆₈Fe₁₅Al₁₅Pd₂, Zr₆₇Fe₁₅Al₅Pd₃,Zr₆₆Fe₁₅Al₁₅Pd₄, Zr₆₅Fe₁₅Al₁₅Pd₅, Zr₆₄Fe₁₅Al₁₅Pd₆, Zr₆₃Fe₁₅Al₁₅Pd₇,Zr₆₂Fe₁₅Al₁₅Pd₈, or by one of the formulas Zr₇₁Fe₁₂Al₁₂Pd₅,

Zr₆₉Fe_(12.85)Al_(12.85)Pd_(5.3), Zr_(66.8)Fe_(13.7)Al_(13.7)Pd_(5.8),Zr₆₅Fe_(14.5)Al_(14.5)Pd₆, Zr_(61.9)Fe_(16.2)Al_(16.2)Pd_(5.7),Zr₅₀Fe₁₂Al₁₂Pd₂₆, Zr_(53.2)Fe_(12.6)Al_(12.6)Pd_(21.6),Zr_(57.6)Fe_(13.95)Al_(13.95)Pd_(14.5), Zr₆₀Fe_(14.3)A_(14.3)Pd_(11.4).

Preferably, the alloy has a structure comprising at least one amorphousphase and at least one crystalline phase. The at least one amorphousphase is preferably obtainable by cooling from a temperature above themelting point of the alloy to a temperature below the glass-transitiontemperature of the amorphous phase at a cooling rate of 1000 K/s orless, i.e., the alloy is preferably a bulk metallic glass.

The present invention is further directed at a method of manufacture ofthe inventive alloys. The method comprises

-   -   preparing a melt of aliquots of A, D, E, G, and optionally Z,        and    -   cooling the melt from a temperature above the melting point to a        temperature below the glass-transition temperature of the        amorphous phase with a cooling rate of 1000 K/s or less to        obtain a solidified material. Preferably, the method comprises        casting of the melt into a mold, in particular, a copper mold.

Alternatively, the inventive alloys may be produced by mechanicalalloying, as described, e.g., in (Eckert J, Mater. Sci. Eng. A 226-228,364 (1997): Mechanical alloying of highly processable glassy alloys).Mechanical alloying means mechanical processing of the alloy or itsconstituents in the solid state, without passing through the liquidstate. In particular, by mechanical alloying of, e.g., a crystallinepowder, an amorphous metallic alloy may be obtained. Suitable mechanicalalloying methods include, but are not restricted to, ball milling. Fordetails, explicit reference is made to the teachings of theabove-mentioned Eckert paper.

The method may additionally comprise a step of processing the alloyabove the glass transition temperature, e.g., for obtaining amixed-phase material. In particular, the method may comprise a step ofheat-treating the solidified material for a few minutes up to 15 hoursat a temperature below the first crystallization temperature or for afew seconds up to 2 hours at a temperature above the firstcrystallization temperature. The first crystallization temperature isthe temperature of the first exothermic feature in a DTA scan of theamorphous alloy when the temperature is raised from the glass transitiontemperature. Heat treatment at relatively low temperatures results inslow kinetics, which is believed to lead to the formation of smallcrystals. For details, see the description of the preferred embodimentsbelow.

For obtaining material with specific surface properties, the alloy maybe subjected to a microstructuring process as described, e.g., in(Kundig A A, Cucinelli M, Uggowitzer P J, Dommann A, Microelectr. Eng.67, 405 (2003): Preparation of high aspect ratio surface microstructuresout of a Zr-based bulk metallic glass) or in the patent applicationPCT/CH 2004/000401. The content of these documents is incorporatedherein by reference in its entirety. Microstructuring may be achieved bycasting the liquid alloy into a mold having itself a microstructuredsurface. For details, reference is made to the teachings of theabove-mentioned Kundig et al. paper and to PCT/CH 2004/000401. In adifferent embodiment, an already solidified alloy is brought into asuperplastic state, i.e, into a state in which it can be easily shaped,by heating the alloy to a temperature above the glass-transitiontemperature, and is pressed onto a microstructured matrix. For details,reference is made to PCT/CH 2004/000401. In an advantageous embodiment,the microstructured mold resp. matrix is a silicon wafer which has beenstructured by etching, as it is well known in the art. In yet anotherembodiment, the liquid alloy is drawn into a system of capillaries bythe capillary effect and rapidly solidified within the capillaries. Fordetails, reference is made to the teachings of the application PCT/CH2004/000401.

The invention is also directed at the use of an inventive alloy for themanufacture of an article destined to be brought into contact with thehuman or animal body. In particular, the invention is directed at theuse of such an alloy for the manufacture of a surgical instrument, ajewelry item, in particular a watch case, or a prosthesis, in particularan endoprosthesis, specifically, a so-called stent. A stent is anendoprosthesis for insertion into a blood vessel, lining the innersurface of the vessel. Stents are used in particular for ensuringsufficient blood flow through the vessel, or for stabilizing the bloodvessel to prevent aneurisms. Other implants for which the inventivealloys can be used are in the field of osteosynthesis, e.g., hipimplants, artificial knees, etc. The present invention is also directedat an endoprosthesis, in particular a stent, manufactured from aninventive alloy.

The inventive alloys are particularly suited for such biomedicalapplications due to their good biocompatibility, high strength and highelasticity. In particular, the inventive alloys of general compositionZr—Cu—Fe—Al or Zr—Fe—Al—Pd are well suited for these purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in connection with anexemplary embodiment illustrated in the drawings, in which

FIG. 1 shows a strongly simplified, schematic phase diagram of a binaryZr—Fe alloy;

FIG. 2 shows a strongly simplified, schematic phase diagram of a binaryCu—Zr alloy;

FIG. 3 shows a strongly simplified, schematic phase diagram of a binaryFe—Al alloy together with the ε-phase;

FIG. 4 shows XRD patterns of as-cast 1 mm×1 cm² alloys of compositionZr_(54.4)Cu_(25.6)Fe₈Al₁₂, Zr₅₈Cu₂₂Fe₈Al₁₂, andZr_(61.6)Cu_(18.4)Fe₈Al₁₂;

FIG. 5 shows SANS intensity data of as-cast 1 mm×1 cm² alloys ofcomposition Zr_(54.4)Cu_(25.6)Fe₈Al₁₂, Zr₅₈Cu₂₂Fe₈Al₁₂, andZr_(61.6)Cu₁₈₄Fe₈Al₁₂ (wave number Q=4π sin θ/λ, with θ=half thescattering angle and λ=wavelength of neutrons);

FIG. 6 shows DTA scans on samples of compositionZr_(54.4)Cu_(25.6)Fe₈Al₁₂, Zr₅₈Cu₂₂Fe₈Al₁₂, Zr_(61.6)Cu_(18.4)Fe₈Al₁₂,and Zr₆₅Al_(7.5)Ni₁₀Cu_(17.5), performed with a heating rate of 20 K/min(T_(g)=glass transition, T_(x1)=first crystallization temperature);

FIG. 7 shows a DTA scan of Zr₅₈Cu₂₂Fe₈Al₁₂, performed with a heatingrate of 20 K/min;

FIG. 8 shows a photograph of cast samples of composition Zr₅₈Cu₂₂Fe₈Al₁₂together with a ruler illustrating their actual size;

FIG. 9 shows XRD patterns of Zr₅₈Cu₂₂Fe₈Al₁₂ cast to cylindrical rods ofdiameters 5, 7 and 8 mm, and to a plate of 1 mm thickness (inset);

FIG. 10 shows DTA scans of Zr₅₈Cu₂₂Fe₈Al₁₂ cast to cylindrical rods ofdiameters 5, 7 and 8 mm (heating rate 20 K/min);

FIG. 11 shows XRD patterns of Zr_(54.4)Cu_(25.6)Fe₈Al₁₂ cast to a conewith outer diameter 6 mm;

FIG. 12 shows a DTA scan of Zr_(61.6)Cu_(18.4)Fe₈Al₁₂, performed with aheating rate of 20 K/min;

FIG. 13 shows a SEM image showing the fracture surface of glassyZr_(61.6)Cu_(18.4)Fe₈Al₁₂;

FIG. 14 shows a room-temperature tensile stress-strain curve of anas-cast cylindrical Zr₅₈Cu₂₂Fe₈Al₁₂ sample with a diameter of 5 mm;

FIG. 15 shows XRD patterns of Zr₅₈Cu₂₂Fe₈Al₁₂ in the as-prepared stateand after annealing for several hours at different temperatures;

FIG. 16 shows an XRD pattern (72 hours scan) of Zr₅₈Cu₂₂Fe₈Al₁₂ afterannealing at 708 K for 12 h. The indexing shows an icosahedral phasewith a lattice constant of 4.76 Å;

FIG. 17 shows DTA scans of Zr₅₈Cu₂₂Fe₈Al₁₂ in the as-prepared state andafter annealing for several hours at different temperatures, asindicated in the figure (heating rate 20 K/min);

FIG. 18 shows SANS intensity data of Zr₅₈Cu₂₂Fe₈Al₁₂ obtained fromin-situ SANS measurements performed at a temperature of 708 K atdifferent times, as indicated in the figure;

FIG. 19 shows the time evolution of the particle size, (D, ofZr₅₈Cu₂₂Fe₈Al₁₂ using the Guinier approximation;

FIG. 20 shows a pseudoternary mixing diagram;

FIG. 21 shows a DTA scan of the alloyZr_(68.3)(Fe_(0.5)Al_(0.5))_(26.8)Pd_(4.9) cast to a thickness of 1 mm;and

FIG. 22 shows an X-ray diffraction pattern of the alloyZr_(68.3)(Fe_(0.5)Al_(0.5))_(26.8)Pd_(4.9) cast to a thickness of 1 mm.

DETAILED DESCRIPTION OF THE INVENTION

Before describing specific examples of inventive alloys and theircharacterization, the concept which led to the development of theinventive alloys shall be described and exemplified.

Many binary alloys which form metallic glasses when splat-cooled havethe composition A₈₀X₂₀, where the atomic radius of A is significantlylarger than that of X. The good glass-forming ability of such alloyswith large size ratio has been explained by topological effects. In thepresent invention, this “80-20 concept” has been generalized toquaternary or higher-component alloys and has been successfully appliedfor developing Ni-free bulk metallic glasses. It has surprisingly beenfound that alloys with exceptionally good glass-forming ability resultwhen following the principles laid down in claim 1. While it isgenerally believed in the art that the presence of nickel improves theglass-forming abilities of an alloy, making nickel an essentialcomponent of many quaternary bulk glass-forming alloys, and especiallyof Zr-based alloys, it has been found by the inventors that nickel canbe dispensed with by following the principles of the present invention,while still alloys with excellent glass-forming abilities are obtained.

While the invention is not limited to the particular compositionsdescribed hereafter, the underlying principles of the invention will inthe following be exemplified for an alloy with general compositionZr—Cu—Fe—Al. Of the four components present in such an alloy, Zr is theelement with the largest atomic size (r=0.160 nm). With Fe (r=0.128 nm),it forms a deep eutectic composition near 20 atomic percent (at. %) Fe.This is illustrated in FIG. 1, which shows, in a highly schematicmanner, part of the phase diagram of a binary Zr—Fe alloy. Thetransitions between the various solid phases have been omitted from thediagram for clarity, such that the diagram shows only the expectedliquidus line, i.e., the liquidus temperature as a function ofcomposition (S=solid, L=liquid). A deep eutectic feature at 24 at. % Feis clearly visible. This deep eutectic can be qualitatively explained bytopological considerations.

Also Zr and Cu have eutectic compositions, one of which occurs at 72.5%Zr, as illustrated in FIG. 2. This diagram shows, again in a highlyschematic fashion, the liquidus line. At various compositions between38.2 at. % and 72.5 at. %, several other eutectics are expected.

The fourth component in the above-mentioned general composition is Al.FIG. 3 shows, again in a highly schematic fashion, part of the phasediagram of a binary Al—Fe alloy. Several solid-solid transitions havebeen included in this diagram. In particular, a high-temperature phase,the so-called ε-phase 301, is present around the composition Al₆Fe₄.This phase prevents a deep eutectic to be present at around 60 at. % inthe Al—Fe phase diagram, which would otherwise be expected byextrapolation, as indicated by the dotted line in FIG. 3. However, sincethe eutectics of Zr₇₆Fe₂₄ and Zr_(72.5)Cu_(27.5) are already below 1000°C., it is likely that the high-temperature ε-phase, which spans atemperature range between 1102 and 1232° C., will not form any more inthe quaternary alloy.

These considerations led to the development of the composition(Zr_(72.5)Cu_(27.5))₈₀(Fe₄₀Al₆₀)₂₀ as a starting point for furtherinvestigations as detailed below. It was found that this alloy, evenwithout any further refinement of the composition, exhibits excellentglass-forming ability. In addition, the composition of the alloy wasvaried, and it was found that the alloy retained its good glass-formingproperties in a rather wide range of compositions.

This shows that the “80-20 concept” can be successfully generalized toquaternary alloys. The concept is believed to be generally applicableand not to be restricted to the particular Zr—Cu—Fe—Al system describedabove. In particular, the same considerations may be applied to alloyswhich are based on Ti, Hf, Nb, La, Pd or Pt as a main component. Insteadof Cu, other elements having a deep eutectic with the main component maybe employed. Particularly good candidates are Be, Ag and Au. The Fecomponent may be replaced by one or more of the transition metals exceptNi, e.g. by Co. The Al component may be replaced by, e.g., Zr or one ormore of the metalloids.

In the following, examples of the manufacture and characterization ofinventive alloys will be given.

EXAMPLE 1 Preparation and Characterization of Amorphous(Zr_(x)Cu_(100−x))₈₀(Fe₄₀Al₆₀)₂₀ Samples

Several Zr-based Ni-free alloys with composition(Zr_(x)Cu_(100−x))₈₀(Fe₄₀Al₆₀)₂₀ were prepared, where x=60, 62, 64, 66,68, 72.5, 77, 79, 81, 83 and 85. Ingots were prepared by arc melting theconstituents (purity >99.9%) in a titanium-gettered argon atmosphere(99.9999% purity). Using an induction-heating coil, the ingots wereremelted in a quartz tube (vacuum ≈10⁻⁵ mbar) and injection cast into acopper mold with high-purity argon. Samples were cast into plates with athickness of 0.5 mm, width of 5 mm and length of 10 mm. To determine thecritical casting thickness, some samples were additionally oralternatively cast into various rod- and cone-like shapes with diametersranging up to 10 mm. Furthermore, several samples were made with athickness of 1 mm and cross section 1 cm×4 cm. The samples were then,where appropriate, cut into various pieces of length 1 cm andinvestigated by X-ray diffraction (XRD), small-angle neutron scattering(SANS), differential thermal analysis (DTA) and/or hardnessmeasurements. XRD was performed with a Scintag XDS-2000x-raydiffractometer, using a collimated monochromatic Cu K_(α) x-ray source.The thermo-physical properties were investigated with a Netzsch ProteusC550 DTA and SANS was performed at Paul Scherrer Institute, Switzerland,using a wavelength of λ=6 Å and sample-detector distances of 1.8 m, 6 m,and 20 m.

FIG. 4 shows XRD patterns of as-cast alloys of compositionZr_(54.4)Cu_(25.6)Fe₈Al₁₂, Zr₅₈Cu₂₂Fe₈Al₁₂, and Zr_(61.6)Cu₁₈₄Fe₈Al₂,i.e., (Zr_(x)Cu_(100−x))₈₀(Fe₄₀Al₆₀)₂₀ with x=68, 72.5, and 77. Allsamples show a typical XRD pattern of an amorphous structure without anyBragg peaks. The amorphicity is also confirmed by SANS. As can be seenin FIG. 5, the same samples do not show any small-angle scattering overa wide Q-range, giving evidence for a homogeneous, amorphous structure.

The DTA scans in FIG. 6, performed with a heating rate of 20 K/min,reveal for all three alloys a clear glass transition, followed by anextended undercooled liquid region and an exothermic crystallizationpeak. For comparison, the Ni-bearing alloy Zr₆₅Al_(7.5)Ni₁₀Cu_(17.5) wasalso investigated by DTA. This result is also shown in FIG. 6 forcomparison. Additionally, the DTA scan in FIG. 7, which was performedover an extended temperature range, shows the endothermic melting peakof Zr₅₈Cu₂₂Fe₈Al₁₂.

Table 2 gives the characteristic values extracted from DTA scans likethose of FIGS. 6 and 7. The glass transition temperatures T_(g) wereextracted from the onset of the endothermic events in FIG. 6 (arrowspointing up) and the first crystallization temperatures T_(x1) wereobtained from the onset of the exothermic peaks (arrows pointing down).The onset of melting T_(m) and the offset of melting T_(l) were obtainedfrom scans like that in FIG. 7. The new Ni-free alloys show anundercooled liquid region ΔT_(x)=T_(x1)−T_(g) of 78 to 86 K and areduced glass transition temperature T_(g)/T_(l) between 0.56 and 0.57.Table 2 lists the ratios of T_(g)/T_(m) also, since in many publicationsthis ratio has been used as the reduced glass transition temperature.The value of T_(g)/T_(m) is 0.59 to 0.62 for the new Ni-free alloys andthus significantly larger than that of Zr₆₅Al_(7.5)Ni₁₀Cu_(17.5).

TABLE 2 Glass transition temperature T_(g), first crystallizationtemperature T_(x1), undercooled liquid region ΔT_(x) = T_(x1) − T_(g),liquidus temperature (offset of melting) T_(l), reduced glass transitiontemperature T_(g)/T_(l), onset of melting T_(m), and ratio T_(g)/T_(m)for three Ni-free alloys and for the Ni-bearing alloyZr₆₅Al_(7.5)Ni₁₀Cu_(17.5), obtained by DTA using a heating rate of 20K/min. Alloy T_(g) (K) T_(x1) (K) ΔT_(x) (K) T_(l) (K) T_(g)/T_(l) T_(m)(K) T_(g)/T_(m) (Zr₆₈Cu₃₂)₈₀(Fe₄₀Al₆₀)₂₀ = Zr_(54.4)Cu_(25.6)Fe₈Al₁₂ 687773 86 1234 0.556 1098 0.62 (Zr_(72.5)Cu_(27.5))₈₀(Fe₄₀Al₆₀)₂₀ =Zr₅₈Cu₂₂Fe₈Al₁₂ 677 761 86 1192 0.568 1130 0.60 (Zr₇₇Cu₂₃)₈₀(Fe₄₀Al₆₀)₂₀= Zr_(61.6)Cu_(18.4)Fe₈Al₁₂ 670 743 78 1189 0.563 1133 0.59Zr₆₅Al_(7.5)Ni₁₀Cu_(17.5) 630 742 112 1165 0.540 1098 0.573

Table 3 shows the Vickers hardness HV of the Ni-free alloys that wasmeasured with a load of 500 g. From these measurements, one obtains anestimated yield strength of 1.56 to 1.68 GPa, using the scaling relationσ_(y)=3 HV. Indeed, detailed tensile tests show a yield strength ofσ_(y)=1.71 GPa and an elastic limit of 2.25% for the alloyZr₅₈Cu₂₂Fe₈Al₁₂.

TABLE 3 Vickers hardness HV (measured with a load of 500 g) andestimated yield strength σ_(y) of the Ni-free alloys. Alloy HV (kg/mm²)σ_(y) (GPa) Zr_(54.4)Cu_(25.6)Fe₈Al₁₂ 563 1.68 Zr₅₈Cu₂₂Fe₈Al₁₂ 542 1.62Zr_(61.6)Cu_(18.4)Fe₈Al₁₂ 521 1.56

Detailed casting experiments were performed on these Ni-free alloys, andthese were compared with the critical casting thicknesses ofZr₆₅Al_(7.5)Ni₁₀Cu_(17.5) and Zr_(52.5)Ti₅Cu_(17.9)Ni_(14.6)Al₁₀(Vit105™) under equal experimental conditions. The alloy Zr₅₈Cu₂₂Fe₈Al₁₂(x=72.5) could be cast into a fully amorphous state up to a rod-diameterof 7 mm. FIG. 8 shows some examples of such cast samples. These examplesprove that indeed articles to be used in real-life applications can bemanufactured from the inventive alloys. The wedge-shaped sample is fullyamorphous up to a diameter of 7 mm.

FIG. 9 shows X-ray diffraction patterns of Zr₅₈Cu₂₂Fe₈Al₁₂ cast tocylindrical rods of diameters 5, 7 and 8 mm, and to a plate of 1 mmthickness (inset). No Bragg peaks are apparent either in the 5 mm rodsample or in the 1 mm plate, while only very weak Bragg peaks seem toarise in the 7 mm rod sample. In contrast, a clear crystalline componentis present in the 8 mm rod sample, as apparent from the strong Braggpeaks from that sample.

These findings are consistent with the DTA scans shown in FIG. 10, whichwere performed on the 5 mm, 7 mm and 8 mm rod samples. Clear exothermiccrystallization peaks are visible for the 5 mm and 7 mm samples, whileno such peak is observed for the 8 mm sample.

Likewise, the alloys with x=68, 77 could be cast in rod shape with adiameter of at least 5 mm with an amorphous structure.

FIG. 11 shows XRD patterns of Zr_(54.4)Cu₂₅₆Fe₈Al₁₂ (x=68) cast to acone with a maximum outer diameter of 6 mm. The XRD scans were performedon 0.5 mm thick plates cut perpendicularly to the longitudinal axis ofthe cone. The average diameter of the corresponding plates is given inthe figure. The XRD patterns of the plates with diameters of 5 mm orless show typical amorphous structures, while the plate with 6 mmdiameter appears to show some Bragg peaks indicating a small volumefraction of crystals in the amorphous matrix. This is perfectlyconsistent with the findings for rods with uniform diameter.

FIG. 12 shows a DTA scan of Zr₆₁₆Cu₁₈₄Fe₈Al₂ (x=77) performed with aheating rate of 20 K/min. Clear glass-transition, crystallization andmelting features are observed. FIG. 13 shows a SEM image, showing thefracture surface of glassy Zr_(61.6)Cu₁₈₄Fe₈A₁₂ (x=77) which is typicalfor an amorphous glass. These findings demonstrate that alsoZr_(61.6)Cu₁₈₄Fe₈Al₁₂ (x=77) is an excellent bulk metallic glass-former.

In summary, of the three alloys with x=68, 72.5 and 77, the alloyZr₅₈Cu₂₂Fe₈Al₁₂ (x=72.5) has the greatest glass-forming ability,comparable to that of Vit105™, followed by Zr_(61.6)Cu₁₈₄Fe₈Al₁₂ andZr_(54.4)Cu_(25.6)Fe₈Al₁₂, followed by the prior-art alloyZr₆₅Al_(7.5)Ni₁₀Cu_(17.5). These experimental results agree well withthe Turnbull theory (D. Turnbull, Contemp. Phys. 10, 473 (1969), F.Spaepen and D. Turnbull, Proc. Sec. Int. Conf. on Rapidly QuenchedMetals (Cambridge, Mass.: M.I.T. Press, 1976), pp. 205-229), whichpredicts that the best glass-forming ability is obtained for the alloywith the highest ratio of T_(g)/T_(l) (see Table 2).

FIG. 14 shows the tensile stress-strain curves of an as-cast cylindricalZr₅₈Cu₂₂Fe₈Al₁₂ (x=72.5) sample with a diameter of 5 mm. Hooke's law iswell fulfilled for strain up to 2.25%. The excellent elasticity and hightensile strength as visible from this diagram are just one example ofthe excellent mechanical properties of the inventive alloys.

The alloys with x=60, 62, 64, 66, 79, 81, 83 and 85 were alsoinvestigated by selected similar methods. It was found that the alloyswith x between 62 and 81 were amorphous when cast to a thickness of 0.5mm, the alloy with x=60 was crystalline, the alloy with x=83 waspartially amorphous, and the alloy with x=85 was crystalline when castto a thickness of 0.5 mm.

It is apparent from this example that the composition of the materialcan be varied within rather broad limits without losing the goodglass-forming properties. Specifically, it may be expected that avariation in the composition with respect to the other constituentelements, in particular a moderate variation of the numbers a and y,will not alter the glass-forming ability dramatically. Furthermore, itis expected that addition of a small amount of an additional componentwill not negatively affect the glass-forming ability or even possiblyimprove the glass-forming ability of the inventive materials, whilepossibly improving certain desired properties.

EXAMPLE 2 Preparation of Mixed-Phase Samples

Samples with a mixed-phase structure were prepared as follows: Fullyamorphous samples of Zr₅₈Cu₂₂Fe₈Al₁₂ were prepared as in Example 1. Thesamples were subjected to heat treatment (annealing) at varioustemperatures for 12 hours. XRD patterns and DTA scans were recorded forthe heat-treated samples. FIG. 15 shows XRD patterns of the samples inthe as-prepared state (bottom trace) and after annealing. The XRDpatterns show typical amorphous structures up to an annealingtemperature of 683 K. At higher annealing temperatures, however, clearBragg peaks arising from an icosahedral phase (I.P.) can be observed. Atstill higher temperatures, peaks which are typical for a Zr₂Fe structureare observed. FIG. 16 shows the XRD pattern of the sample annealed at708 K for 12 hours in more detail. The indexing indicates the presenceof an icosahedral phase with a lattice constant of 0.476 nm. FIG. 17shows DTA scans of the same samples as in FIG. 15, which are consistentwith the development of a structure with both glassy and crystallinecomponents.

In order to better characterize the structure after annealing, in-situsmall-angle neutron scattering (SANS) experiments were performed duringannealing at a temperature of 708 K of a Zr₅₈Cu₂₂Fe₈Al₁₂ sample whichwas initially fully amorphous. The results are shown in FIG. 18, fortotal annealing times as indicated. The results show that crystallineregions develop in the initially fully amorphous sample, with typicalsizes on the order of only nanometers. These data were analyzed byapplying the Guinier approximation. FIG. 19 shows the time evolution ofthe particle size, (D, in this approximation. This clearly demonstratesthe emergence of nanocrystals within the glassy matrix. It is believedthat the generation of such nanocrystals is fostered by keeping theannealing temperature only slightly above the laboratory glasstransition temperature, in particular, in a range between 0 and 150 Kabove the laboratory glass transition temperature. The laboratory glasstransition temperature is to be understood as the glass transitiontemperature as determined by DSC (differential scanning calorimetry)with a typical heating rate of 20 K/min. Higher annealing temperaturesoften lead to the precipitation of larger crystals; for example in therange of 0.1-20 μm.

Such mixed-phase materials exhibit somewhat different mechanicalproperties than a fully glassy material. In particular, ductility isoften improved, which can be rationalized by the fact that shear bandswhich develop as a result of shear forces during forming and which mightlead to breaking of the material are disrupted by the crystals. Theseproperties may be particularly beneficial in applications where thematerial must be shaped or deformed during manufacture of the endproduct.

EXAMPLE 3 Variations of Composition

Samples in a widely varying range of compositions were prepared andinvestigated. The compositions of the following Tables proved to be atleast partially amorphous when cast to a plate with thickness of 1 mm(Table 4), 0.5 mm (table 5), or 0.2 mm (Table 6):

TABLE 4 Alloys having a partially or fully amorphous structure when castto a thickness of 1 mm. (Zr₉₅Ti₅)₇₂Cu₁₃Fe₁₃Al₂ Zr₇₂Cu₁₂Fe₁₂Al₄Zr₇₀Cu₁₃Fe₁₃Al₃Sn₁ Zr₇₀Cu₁₃Fe₁₃Al₄ Zr₇₀Cu₁₃Fe₁₃Al₂Cr₂ Zr₇₂Cu₁₁Fe₁₁Al₆Zr₇₀Cu₁₃Fe₁₃Al₂Nb₂ Zr₇₂Cu_(11.5)Fe₁₁Al_(5.5) Zr₇₀Cu₁₃Fe₁₃Al₂Zn₂Zr₇₃Cu₁₁Fe₁₁Al₅ (Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈Mo₂ Zr₇₁Cu₁₁Fe₁₁Al₇(Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈P₂ Zr₆₉Cu₁₁Fe₁₁Al₉ (Zr₉₅Hf₅)₇₂Cu₁₃Fe₁₃Al₂Zr₇₀Cu_(10.5)Fe_(10.5)Al₉ Zr₇₀Cu₁₁Fe₁₁Al₈ Zr₇₀Cu₁₀Fe₁₁Al₉Zr₇₁Cu₁₁Fe₁₀Al₈ Zr₇₀Cu₁₁Fe₁₀Al₉ (Zr₇₄Cu₁₃Fe₁₃)₉₀Al₁₀ Zr₆₉Cu₁₀Fe₁₀Al₁₁Zr₇₂Cu₁₃Fe₁₃Al₂ Zr₆₉Cu₁₀Fe₁₁Al₁₀ (Zr₇₄Cu₁₃Fe₁₃)₉₈Al₂ Zr₇₀Cu₁₃Fe₁₃Al₂Sn₂Zr₇₃Cu₁₃Fe₁₃Al₁ Zr₇₂Cu₁₃Fe₁₃Sn₂ Zr₇₂Cu₁₃Fe₁₃Al₂ (Zr₇₄Cu₁₃Fe₁₃)₉₈Sn₂Zr₇₁Cu₁₃Fe₁₃Al₃

TABLE 5 Alloys with a partially or fully amorphous structure when castto a thickness of 0.5 mm. (Zr₇₉Cu₂₁)₈₀(Fe₄₀Al₆₀)₂₀(Zr₆₆Cu₃₄)₈₀(Fe₄₀Al₆₀)₂₀ (Zr₈₁Cu₁₉)₈₀(Fe₄₀Al₆₀)₂₀(Zr₆₄Cu₃₆)₈₀(Fe₄₀Al₆₀)₂₀ (Zr₈₃Cu₁₇)₈₀(Fe₄₀Al₆₀)₂₀(Zr₆₂Cu₃₈)₈₀(Fe₄₀Al₆₀)₂₀

TABLE 6 Alloys with a partially or fully amorphous structure when castto a thickness of 0.2 mm. Zr₇₂Cu₁₃Fe₁₃Al₂ (Zr₇₄Cu₁₃Fe₁₃)₉₈Ge₂Zr₇₂Cu₁₃Fe₁₃Sn₂ (Zr₇₄Cu₁₃Fe₁₃)₉₈Sn₂

For comparison, the alloys in Table 7, while being binary, ternary orNi-containing alloys, were also investigated and developed an at leastpartially amorphous structure when cast to a thickness of 0.2 mm.

TABLE 7 Comparative listing of other alloys with a partially or fullyamorphous structure when cast to a thickness of 0.2 mm.Zr₇₀Cu₁₃Fe₁₃Al₂Ni₂ Zr₇₆Fe₂₀Al₄ Zr₇₀Cu_(6.5)Fe₁₃Al₂Ni_(6.5) Zr₇₀Fe₂₇Nb₃(Zr₇₄Cu₁₃Fe₁₃)₉₈Ni₂ Zr₆₈Fe₂₇Nb₅ (Zr₇₄Cu₁₃Fe₁₃)₉₆Ni₄ Zr₆₆Fe₂₈Nb₆ Zr₇₆Fe₂₄Zr₆₈Fe₂₅Nb₇ Zr₇₅Fe₂₃Sn₂ Zr₇₅Fe₂₄Ni₁ Zr₇₀Fe₂₈Nb₂ Zr_(75.5)Fe_(23.5)Ge₁Zr₇₆Fe₂₂Sn₂ Zr₇₀Fe₂₈Nb₁Sn₁ Zr₇₆Fe₂₃Sn₁ Zr_(75.5)Fe_(23.5)Si₁ Zr₇₅Fe₂₄Sn₁Zr₇₇Fe₂₃ Zr₇₄Fe₂₄Sn₂ Zr₆₉Fe₃₀Nb₁ Zr_(73.72)Fe_(23.28)Sn₃ Zr₆₈Fe₃₁Nb₁Zr₇₃Fe₂₄Sn₃ Zr₇₅Fe₂₅ Zr₇₆Fe₂₁Sn₃ Zr₆₈Fe₂₆Nb₆ Zr₆₉Fe₂₉Nb₁Sn₁ Zr₆₉Fe₂₇Nb₄Zr_(75.5)Fe_(23.5)Al₁ Zr₆₈Fe₂₈Nb₄ Zr₇₆Fe₂₃Al₁ Zr₇₁Fe₂₆Nb₃ Zr₇₂Fe₂₈Zr₇₀Fe₂₈Nb₂ Zr₇₄Fe₂₆ Zr₇₀Fe₂₆Nb₄ Zr₇₀Fe₂₉Nb₁ Zr₇₄Fe₁₃Cu₁₃ Zr₇₂Fe₂₇Nb₁Zr₇₁Fe₁₆Cu₁₃ Zr₇₄Fe₂₅Nb₁ Zr₇₄Fe₁₃Cu₁₃ Zr₇₃Fe₂₅Nb₂ Zr₇₆Fe₂₃Cu₁ Zr₇₆Ni₂₄Zr₇₆Fe₁₂Cu₁₂ Zr₆₀Fe₂₀Ni₂₀ Zr_(73.5)Fe_(21.5)Cu₅ Zr_(75.5)Fe_(23.5)Si₁Zr₇₂Fe₁₄Cu₁₄ Zr₇₆Fe₁₆Al₈

Specifically, this list shows that also ternary, nickel-free alloys canbe reasonably good glass-formers, especially if composed according tothe “80:20 scheme”. Specifically, the list shows that ternary alloys ofcomposition (Zr_(x)D_(100−x))_(a)Fe_(100−a), where the number a is inthe range from about 70 to about 90, in particular approximately 80, aregood glass formers. Here D is advantageously Cu, Nb, Al or Sn.

The alloys in Table 8 have also been prepared and were found to be fullyamorphous when subjected to splat cooling to a thickness of 20micrometers at high cooling rates of approximately 10⁶ K/s. These alloysmay be regarded as candidate materials for bulk metallic glasses, whilecasting experiments will be necessary to verify which of these areindeed bulk metallic glasses.

TABLE 8 Alloys having a fully amorphous structure when splat-cooled. Allnumbers are atomic percentages. Zr₅₈Cu₂₂Fe₁₈Al₂ (Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Nb₂Zr₅₈Cu₂₂Fe₁₆Al₄ (Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Ta₂ Zr₅₈Cu₂₂Fe₁₄Al₆(Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Cr₂ Zr₅₈Cu₂₂Fe₁₂Al₈ (Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Co₂Zr₅₈Cu₂₂Fe₁₀Al₁₀ (Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Mo₂ Zr₅₈Cu₂₂Fe₆Al₁₄(Zr₅₈Cu₂₂Fe₈Al₁₂)₉₈Sn₂ Zr₅₈Cu₂₂Fe₄Al₁₆ Zr₅₈Cu₂₂Fe₆Al₁₂Nb₂Zr₅₈Cu₂₂Fe₂Al₁₈ (Zr_(72.5)Cu_(27.5))₇₆Fe₈Al₁₂Nb₄Zr_(62.4)Co_(17.6)Fe₈Al₁₂ Zr₅₈Cu₂₂Fe₄Al₁₂Nb₄ Zr₆₅Al₁₅Fe₁₅Nb₅Zr₅₈Cu₂₂Fe₈Al₁₀Nb₂ Zr₅₈Cu₂₂Co₈Al₁₂ (Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Co₂Zr₆₈Al₁₅Fe₁₅Nb₂ (Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Cr₂(Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Nb₂ (Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Ta₂(Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Sn₂ (Zr_(72.5)Cu_(27.5))₇₈Fe₈Al₁₂Mo₂(Zr_(72.5)Cu_(27.5))₈₀Fe₆Al₁₂Nb₂ (Zr_(72.5)Cu_(27.5))₇₆Fe₈Al₁₂Sn₄

Also the ternary and binary alloys in Table 9 were found to be fullyamorphous when splat-cooled. These are listed for comparative purposes.

TABLE 9 Ternary and binary alloys having a fully amorphous structurewhen splat-cooled. Zr₆₀Fe₁₅Al₁₅ Zr₅₈Cu₂₂Fe₂₀ Zr₇₅Fe₂₃Sn₂ Zr₅₈Cu₂₂Al₂₀Zr₇₀Fe₂₈Nb₂ Nb₆₀Co₄₀

The wide range of alloys according to the present invention which wereinvestigated in these experiments clearly demonstrate that widevariations of composition are possible without losing the glass-formingproperties of the alloys.

EXAMPLE 4 Biocompatibility Tests

As an example of the newly developed Ni-free alloys, the cytotoxicity ofthe alloy Zr₅₈Cu₂₂Fe₈Al₁₂ was determined. The effect of surfacemodification by passivation in diluted nitric acid was alsoinvestigated.

Surface analysis using XPS showed that a natural oxide layer, composedalmost exclusively of zirconium oxide, forms on the surface on thisglass and that it has a thickness of 7-8 nm. This layer protects mousefibroblasts used in the study from the toxic metals, especially Cu,present in the bulk, allowing for good cell growth on the alloy. Theresults of indirect tests demonstrate that this layer is stable in PBS(phosphate-buffered solution) for many weeks, and that no toxic effectsdue to high ion concentrations diffusing into the medium occur.

The thickness of the zirconia layer is only slightly increased bypassivation with nitric acid. However, this treatment clearly improvesthe quality of the surface layer, which leads to increased corrosionresistance and lower diffusion of bulk elements into the medium, andthus to improved biocompatibility. After this passivation treatment, thealloy shows cell growth comparable to that on polystyrene, which is usedhere as a negative control.

In conclusion, the cytotoxic properties of the metallic glasses of thepresent invention are very promising and thus indicate a very goodbiocompatibility.

EXAMPLE 5 Cu- and Ni-Free Alloys

As Cu may nevertheless be problematic in many medical applications, asearch for Cu-free alloys was conducted. Starting from the Zr—Cu—Fe—Albulk metallic glasses of the previous examples, Pd (palladium) was foundto be promising in replacing Cu in such alloys. For a systematic searchfor bulk metallic glasses, alloys belonging to the pseudoternaryZr—(Fe_(0.5)Al_(0.5))—Pd system were screened. Initially, the amount ofPd was varied between 0% and approximately 22% in a pseudotemaryZr—(Fe_(0.5)A_(0.5))—Pd system along the (Fe_(0.5)Al_(0.5))₃₀ line,while choosing the ratio of the sums of the atomic percentages of Zr andFe on the one hand and Al and Pd on the other hand roughly according tothe 80:20 concept. In this manner, a number of initial alloycompositions with favorable glass-forming properties were identified.The composition was then varied around these initial compositions in aniterative manner within the range of pseudoternaryZr—(Fe_(0.5)Al_(0.5))—Pd compositions.

The following tables summarize the results found in theseinvestigations.

TABLE 10 Cu-free Zr—Fe—Al—Pd alloys having a partially or fullyamorphous structure when cast to a thickness of 3 mmZr₆₇Fe_(13.2)Al_(13.2)Pd_(6.6) Zr_(69.7)Fe_(12.95)Al_(12.95)Pd_(4.4)Zr_(66.7)Fe_(14.45)Al_(14.45)Pd_(4.4)

TABLE 11 Cu-free Zr—Fe—Al—Pd alloys having a partially or fullyamorphous structure when cast to a thickness of 1 mmZr_(68.3)Fe_(13.4)Al_(13.4)Pd_(4.9)Zr_(65.4)Fe_(14.85)Al_(14.85)Pd_(4.9)Zr_(62.3)Fe_(16.7)Al_(16.7)Pd_(4.3) Zr_(59.2)Fe_(18.3)Al_(18.3)Pd_(4.2)Zr₇₂Fe_(11.5)Al_(11.5)Pd₅ Zr_(73.4)Fe_(10.9)Al_(10.9)Pd_(4.8)Zr_(75.2)Fe_(10.2)Al_(10.2)Pd_(4.3) Zr₇₇Fe_(9.5)Al_(9.5)Pd₄Zr_(67.9)Fe_(11.8)Al_(11.8)Pd_(8.5) Zr₆₅Fe_(11.4)Al_(11.4)Pd_(12.2)Zr_(62.5)Fe_(10.75)Al_(10.75)Pd₁₆

TABLE 12 Cu-free Zr—Fe—Al—Pd alloys having a partially or fullyamorphous structure when cast to a thickness of 0.5 mmZr_(69.5)Fe₁₅Al₁₅Pd_(0.5) Zr₆₉Fe₁₅Al₁₅Pd₁ Zr₆₈Fe₁₅Al₁₅Pd₂Zr₆₇Fe₁₅Al₁₅Pd₃ Zr₆₆Fe₁₅Al₁₅Pd₄ Zr₆₅Fe₁₅Al₁₅Pd₅ Zr₆₄Fe₁₅Al₁₅Pd₆Zr₆₃Fe₁₅Al₁₅Pd₇ Zr₆₂Fe₁₅Al₁₅Pd₈ Zr₇₁Fe₁₂Al₁₂Pd₅Zr₆₉Fe_(12.85)Al_(12.85)Pd_(5.3) Zr_(66.8)Fe_(13.7)Al_(13.7)Pd_(5.8)Zr₆₅Fe_(14.5)Al_(14.5)Pd₆ Zr_(61.9)Fe_(16.2)Al_(16.2)Pd_(5.7)Zr₅₀Fe₁₂Al₁₂Pd₂₆ Zr_(53.2)Fe_(12.6)Al_(12.6)Pd_(21.6)Zr_(57.6)Fe_(13.95)Al_(13.95)Pd_(14.5) Zr₆₀Fe_(14.3)Al_(14.3)Pd_(11.4)

The examples of Tables 10, 11 and 12 are indicated by black squares inthe pseudotemary mixing diagram of FIG. 20. From this diagram, it may beappreciated that alloys containing at least 50 at.-% Zr, at least 0.5at.-% Pd and at least 19 at.-% of a mixture of Fe and Al inapproximately equal atomic proportions are expected to be good glassformers. This is even more true for alloys of this type containing atleast approximately 59 at.-% of Zr, up to approximately 36 at.-% of theFe—Al mixture and/or at least approximately 4 at.-% Pd. In particular,all alloys in the trapezoidal area indicated in FIG. 20 may reasonablybe expected to be good glass formers. Small variations of the relativeproportions between Fe and Al within a few percent, say, between 60:40and 40:60 or better between 55:45 and 45:55, are not expected tostrongly affect the glass-forming ability.

Notably, all alloys in Tables 10 and 11 and most of the alloys in Table12 correspond to the 80:20 principle in the following sense: The ratioof the sum of the atomic percentages of Zr and Fe to the sum of theatomic percentages of Al and Pd is approximately 80:20. In the examplesof Tables 10 and 11, the ratio of the atomic content of Zr+Fe to that ofAl+Pd varies between approximately 73:27 and approximately 87:13. The80:20 principle is fulfilled to an excellent degree for the alloys inTable 10, i.e., for those alloy compositions which have been found tohave the highest critical casting thickness. There, the correspondingratio varies between approximately 80:20 and approximately 83:17.

Concerning the variations within the Zr—Fe subsystem, in the preferredcompositions of Tables 10 and 11, the ratio of the atomic percentage ofZr to the atomic percentage of Fe is in the range between approximately76:24 and approximately 89:11. It appears that this is a preferredrange. In particular, in the examples of Table 10, this ratio variesbetween approximately 81:19 and approximately 85:15. In contrast, theratio between Al and Pd may apparently vary in a wider range withoutdetrimental effects on the glass-forming ability of the alloy. In theexamples of Tables 10 and 11, the ratio of the atomic percentage of Alto the atomic percentage of Pd varies between approximately 40:60 andapproximately 82:18. In particular, in the examples of Table 10, thisratio varies between approximately 65:35 and approximately 78:22.

An even improved biocompatibility may be achieved by replacing Pd partlyor fully by Pt (platinum) in the above examples. Pt (platinum) has verysimilar properties as Pd, such as outer electronic structure, inconsequence, similar chemical properties, and almost the sameGoldschmidt radius. Therefore, a partial or full replacement of Pd by Ptwill not strongly alter the mechanical properties of the alloy or itsglass-forming ability.

As an example of measurements performed on the Cu-free alloys, FIG. 21shows a DTA scan and FIG. 22 shows an X-ray diffraction pattern, using aCoK_(α) X-ray source, of the alloyZr_(68.3)(Fe_(0.5)Al_(0.5))_(26.8)Pd_(4.9) cast to a thickness of 1 mm.The DTA scan exhibits a clear glass transition and a secondcrystallization event, while the X-ray diffraction pattern exhibits thebroad hump indicative of an amorphous material.

Also the following Cu-free alloys were found to be at least partiallyamorphous when cast to a thickness of 0.5 mm:

Zr₆₉Fe₁₅Al₁₅Y₁, Zr_(68.5)Fe₁₅Al₁₅Y_(1.5).

In these examples, Pd has been replaced by Y (yttrium).

A further example of an alloy found to be at least partially amorphouswhen cast to a thickness to 0.2 mm is Zr₇₀Fe₂₈Nb₁Sn₁.

It is to be understood that the above examples are only provided forillustrative purposes and that the invention is in no way limited tothese examples.

LIST OF ABBREVIATIONS, SYMBOLS AND REFERENCE SIGNS

-   at. % atomic percent-   XRD X-ray diffraction-   SEM scanning electron microscopy-   SANS small-angle neutron scattering-   DTA differential thermal analysis-   DSC differential scanning calorimetry-   T_(g) glass transition temperature-   T_(x1) first crystallization temperature-   ΔT_(x) undercooled liquid region-   T_(l) offset of melting (liquidus temperature)-   T_(m) onset of melting-   T temperature-   σ_(y) yield strength-   HV Vickers hardness-   S solid-   L liquid-   2θ scattering angle-   Int intensity-   a.u. arbitrary units-   Q wave number-   S(Q) scattering intensity-   q heat transfer-   cps counts per second-   σ tensile stress-   ε strain-   I.P. icosahedral phase-   ann. annealed-   Φ particle size

1-42. (canceled)
 43. An alloy having a structure containing at least oneamorphous phase, the alloy being represented by the general formula[(Zr_(x)Cu_(100−x))_(a)(E_(y)G_(100−y))_(100−a)]_(100−b)Z_(b), whereina, b, x and y are real numbers signifying atomic percentages with70≦a≦90, x≧50, y>0, and 0≦b≦6, wherein E is selected from the groupconsisting of Fe and Co, wherein G and Z are components each consistingof at least one element, wherein all elements in E, G and Z are mutuallydifferent and different from Zr and Cu, and wherein said alloy issubstantially free of nickel, with the proviso that, if E=Al, then G≠Pd.44. The alloy according to claim 43, wherein G is at least one elementselected from the group consisting of Al (aluminum) and the metalloids.45. The alloy according to claim 43, wherein E is Fe (iron) and G is Al(aluminum).
 46. The alloy according to claim 43, wherein 30≦y≦50. 47.The alloy according to claim 43, wherein 62≦x≦83.
 48. The alloyaccording to claim 43, wherein the alloy is essentially represented bythe formula (Zr_(x)Cu_(100−x))₈₀(Fe₄₀Al₆₀)₂₀ with 62≦x≦83.
 49. The alloyaccording to claim 48, wherein x is substantially selected from thenumbers 62, 64, 66, 68, 72.5, 77, 79, 81 or
 83. 50. An alloysubstantially represented by one of the formulas (Zr₉₅Ti₅)₇₂Cu₁₃Fe₁₃Al₂,Zr₇₀Cu₁₃Fe₁₃Al₃Sn₁, Zr₇₀Cu₁₃Fe₁₃Al₂Cr₂, Zr₇₀Cu₁₃Fe₁₃Al₂Nb₂,Zr₇₀Cu₁₃Fe₁₃Al₂Zn₂, (Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈Mo₂, (Zr₇₂Cu₁₃Fe₁₃Al₂)₉₈P₂,(Zr₉₅Hf₅)₇₂Cu₁₃Fe₁₃Al₂, Zr₇₀Cu₁₁ Fe₁₁Al₈, Zr₇₁Cu₁₁Fe₁₀Al₈,(Zr₇₄Cu₁₃Fe₁₃)₉₀Al₁₀, Zr₇₂Cu₁₃Fe₁₃Al₂, (Zr₇₄Cu₁₃Fe₁₃)₉₈Al₂,Zr₇₃Cu₁₃Fe₁₃Al₁, Zr₇₂Cu₁₃Fe₁₃Al₂, Zr₇₁Cu₁₃Fe₁₃Al₃, Zr₇₂Cu₁₂Fe₁₂Al₄,Zr₇₀Cu₁₃Fe₁₃Al₄, Zr₇₂Cu₁₁ Fe₁₁Al₆, Zr₇₂Cu_(11.5)Fe₁₁Al_(5.5),Zr₇₃Cu₁₁Fe₁₁Al₅, Zr₇₁Cu₁₁Fe₁₁Al₇, Zr₆₉Cu₁₁Fe₁₁Al₉,Zr₇₀Cu_(10.5)Fe_(100.5)Al₉, Zr₇₀Cu₁₀Fe₁₁Al₉, Zr₇₀Cu₁₁Fe₁₀Al₉,Zr₆₉Cu₁₀Fe₁₀Al₁₁, Zr₆₉Cu₁₀Fe₁₁Al₁₀, Zr₇₀Cu₁₃Fe₁₃Al₂Sn₂, Zr₇₂Cu₁₃Fe₁₃Sn₂,(Zr₇₄Cu₁₃Fe₁₃)₉₈Sn₂, (Zr₇₉Cu₂₁)₈₀(Fe₄₀Al₆₀)₂₀, (Zr₈₁Cu₁₉)₈₀(Fe₄₀Al₆₀)₂₀, (Zr₈₃Cu₁₇)₈₀(Fe₄₀Al₆₀)₂₀, (Zr₆₆Cu₃₄)₈₀(Fe₄₀Al₆₀)₂₀,(Zr₆₄Cu₃₆)₈₀(Fe₄₀Al₆₀)₂₀, and (Zr₆₂Cu₃₈)₈₀(Fe₄₀Al₆₀)₂₀.
 51. An alloyhaving a structure containing at least one amorphous phase, the alloybeing represented by the general formula[(Zr_(x)Fe_(100−x))_(a)(Al_(y)G_(100−y))_(100−a)]_(100−b)Z_(b), whereina, b, x and y are real numbers signifying atomic percentages with70≦a≦90, x≧50, y>0, and 0≦b≦6, wherein G is at least one elementselected from the group consisting of Pt and Pd, wherein Z is acomponent consisting of at least one element, wherein all elements in Gand Z are mutually different and different from Zr, Fe and Al, andwherein said alloy is substantially free of copper and nickel.
 52. Thealloy according to claim 51, wherein G is Pd (palladium).
 53. The alloyaccording to claim 51, wherein the atomic percentages of Fe and Al aresubstantially equal.
 54. The alloy according to claim 51, wherein68≦x≦89 and 73≦a≦87.
 55. The alloy according to one claim 51, wherein40≦y≦82.
 56. The alloy according to claim 51, wherein 81≦x≦85, 80≦a≦83,and 65≦y≦80.
 57. The alloy according to one of claims 43 and 51, wherein0≦b≦2.
 58. The alloy according to one of claims 43 and 51, wherein b>0,and wherein Z is at least one element selected from the group consistingof Ti, Hf, V, Nb, Y, Cr, Mo, Fe, Co, Sn, Zn, P, Pd, Ag, Au and Pt. 59.The alloy according to one of claims 43 and 51, wherein b=0.
 60. Analloy having a structure containing at least one amorphous phase, thealloy being substantially represented by the general formulaZr_(i)(Fe_(50+ε)Al_(50−ε))_(j)X_(k), wherein X is one or more elementsselected from the group consisting of Pd and Pt, wherein i, j, k and εare real numbers signifying atomic percentages, and wherein −10≦ε≦10,i≧50, j≧19, k≧0.5 and i+j+k=100.
 61. The alloy according to claim 60,wherein X is Pd (palladium).
 62. The alloy according to claim 60,wherein 62≦i≦77.
 63. The alloy according to claim 60, wherein 19≦j≦34.64. The alloy according to claim 60, wherein −2≦ε≦2.
 65. The alloyaccording to claim 60, wherein ε is substantially zero, 66≦i≦70, 25≦j≦29and 4≦k≦7.
 66. An alloy having the features of both claim 51 and claim60.
 67. An alloy substantially represented by one of the formulasZr₆₇Fe_(13.2)Al_(113.2)Pd_(6.6), Zr_(69.7)Fe_(12.95)Al_(12.95)Pd_(4.4),Zr_(66.7)Fe_(14.45)Al_(14.45)Pd_(4.4),Zr_(68.3)Fe_(13.4)Al_(113.4)Pd_(4.9),Zr_(65.4)Fe_(14.85)Al_(14.85)Pd_(4.9),Zr_(62.3)Fe_(16.7)Al_(16.7)Pd_(4.3),Zr_(59.2)Fe_(18.3)Al_(18.3)Pd_(4.2), Zr₇₂Fe_(11.5)A_(11.5)Pd₅,Zr_(73.4)Fe_(10.9)Al_(10.9)Pd_(4.8),Zr_(75.2)Fe_(10.2)Al_(10.2)Pd_(4.3), Zr₇₇Fe_(9.5)Al_(9.5)Pd₄,Zr_(67.9)Fe_(11.8)Al_(11.8)Pd_(8.5. Zr) ₆₅Fe_(11.4)Al_(11.4)Pd_(12.2),Zr_(62.5)Fe_(10.75)Al_(10.75)Pd₁₆, Zr_(i)(Fe₅₀Al₅₀)₃₀Pd_(70−i) with62≦i≦69.5, Zr_(69.5)Fe₁₅Al₁₅Pd_(0.5), Zr₆₉Fe₁₁₅Al₁₅Pd_(0.5),Zr₆₈Fe₁₅Al₁₅Pd₂, Zr₆₇Fe₁₅Al₁₅Pd₃, Zr₆₆Fe₁₅Al₁₅Pd₄, Zr₆₅Fe₁₅Al₁₅Pd₅,Zr₆₄Fe₁₁₅Al₁₅Pd₆, Zr₆₃Fe₁₅Al₁₅Pd₇, Zr₆₂Fe₁₅Al₁₅Pd₈, Zr₇₁Fe₁₂Al₁₂Pd₅,Zr₆₉Fe_(12.85)Al_(12.85)Pd_(5.3), Zr_(66.8)Fe_(13.7)Al_(13.7)Pd_(5.8),Zr₆₅Fe_(14.5)Al_(14.5)Pd₆, Zr_(61.9)Fe_(16.2)Al_(16.2)Pd_(5.7),Zr₅₀Fe₁₂Al₁₂Pd₂₆, Zr_(53.2)Fe_(12.6)Al_(12.6)Pd_(21.6),Zr_(57.6)Fe_(13.95)Al_(13.95)Pd_(14.5), andZr₆₀Fe_(14.3)Al_(14.3)Pd_(11.4).
 68. The alloy according to one ofclaims 43, 51 and 60, wherein the alloy has a structure comprising atleast one amorphous phase and at least one crystalline phase.
 69. Thealloy according to one of claims 43, 51 and 60, wherein said at leastone amorphous phase is obtainable by cooling from a temperature abovethe melting point of the alloy to a temperature below theglass-transition temperature of the amorphous phase at a cooling rate of1000 K/s or less.
 70. A method of manufacturing an alloy, the methodcomprising: preparing a melt of aliquots of all components of(Zr_(x)Cu_(100−x))_(a)(E_(y)G_(100−y))_(100−a)]_(100−b)Z_(b), andcooling the melt from a temperature above the melting point of the alloyto a temperature below the glass-transition temperature of the amorphousphase with a cooling rate of 1000 K/s or less to obtain a solidifiedmaterial, wherein a, b, x and y are real numbers signifying atomicpercentages with 70≦a≦90, x≧50, y>0, and 0≦b≦6, wherein E is selectedfrom the group consisting of Fe and Co, wherein G and Z are componentseach consisting of at least one element, wherein all elements in E, Gand Z are mutually different and different from Zr and Cu, and whereinsaid alloy is substantially free of nickel, with the proviso that, ifE=Al, then G≠Pd.
 71. A method of manufacturing an alloy, the methodcomprising: preparing a melt of aliquots of all components of[(Zr_(x)Fe_(100−x))_(a)(Al_(y)G_(100−y))_(100−a)]_(100−b)Z_(b), andcooling the melt from a temperature above the melting point of the alloyto a temperature below the glass-transition temperature of the amorphousphase with a cooling rate of 1000 K/s or less to obtain a solidifiedmaterial, wherein a, b, x and y are real numbers signifying atomicpercentages with 70≦a≦90, x≧50, y>0, and 0≦b≦6, wherein G is at leastone element selected from the group consisting of Pt and Pd, wherein Zis a component consisting of at least one element, wherein all elementsin G and Z are mutually different and different from Zr, Fe and Al, andwherein said alloy is substantially free of copper and nickel.
 72. Amethod of manufacturing an alloy, the method comprising: preparing amelt of aliquots of all components ofZr_(i)(Fe_(50+ε)Al_(50−ε))_(j)X_(k), and cooling the melt from atemperature above the melting point of the alloy to a temperature belowthe glass-transition temperature of the amorphous phase with a coolingrate of 1000 K/s or less to obtain a solidified material, wherein X isone or more elements selected from the group consisting of Pd and Pt,wherein i, j, k and ε are real numbers signifying atomic percentages,and wherein −10≦ε≦10, i≧50, j≧19, k≧0.5 and i+j+k=100.
 73. The methodaccording to one of claims 70, 71 and 72, the method comprising castingthe melt into a mold, in particular into a microstructured mold.
 74. Themethod according to one of claims 70, 71 and 72, the method comprisingheat-treating the solidified material at a temperature below the onsettemperature of melting for a time period sufficient for the formation ofat least one crystalline phase.
 75. The method according to one ofclaims 70, 71, and 72, the method comprising a step of bringing thealloy into a superplastic state and forming a microstructure in thisstate.
 76. Use of an alloy according to one of claims 43, 51 and 60 formanufacturing a product intended for being brought into prolongedcontact with a human or animal body.
 77. An implant for implantation inthe human or animal body comprising an alloy according to one of claims43, 51 and 60.